Toothed power transmission belt

ABSTRACT

A power transmission belt having a body with a length, a width between laterally spaced sides, and a thickness between inside and outside surfaces. At least one load carrying member extends in a lengthwise direction. The body has a plurality of teeth spaced along at least one of the inside and outside of the body. The teeth have a width that decreases progressively from: a) a first location between the inside and outside surfaces; and b) one of the inside and outside surfaces so that the one surface has a width that is less than a width of the other surfaces. A cloth layer is applied to the one surface and is a multiwoven structure with interwoven: a) warp; and b) at least two different wefts.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.12/214,690 filed Jun. 20, 2008.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to power transmission belts and, moreparticularly, to a power transmission belt with pulley engaging teethspaced along the length of the belt.

2. Background Art

It is known to make power transmission belts from rubber with teethspaced at regular intervals along the length of the belt. These beltsare commonly used in high load applications, as in association withengines and other driving/driven devices. It is also known toincorporate and embed in these belts load carrying members, that extendlengthwise of the belt. A cloth layer is commonly placed over a surfaceof the belt upon which the teeth are formed. Exemplary of such aconstruction is that shown in Gazette of Japanese Patent Laid-Open2002/168,302.

In this type of toothed belt, high modulus properties are demanded tomaintain engagement of the teeth with a complementarily-shaped andcooperating pulley, even under high load applications. To achieve thisobjective, it is known to make the cross-sectional area of the loadcarrying members relatively large. The load carrying members are oftenmade for this high load application by twisting together a plurality ofundertwisted cords that together produce the elongate load carryingmember. These load carrying members have been made with high modulusfiber, such as glass fiber, carbon fiber, aramid fiber, and PBO fiber.

The use of twisted load carrying members that have a large diameter andthat utilize high modulus fiber in a toothed belt has resulted in atleast two notable problems. First of all, such belts are prone to havingless than satisfactory bending fatigue characteristics. Secondly, thesebelts tend to experience an initial, potentially detrimental, increasein elongation that results by a tightening of the twisted components ofthe load carrying members upon running the belt under a high load.

Less than desired bending fatigue properties may cause the followingresults. Deterioration, resulting from bending increases as the bendingrepetitions of load carrying members, resulting from engagement withpulleys in operation, increases. This causes elongation of the loadcarrying members, as a result of which the tension in the belt may bedetrimentally lowered. As this occurs, the belt may be prone topremature breakage in a manner by other than separation of the teeth.

As to the second problem, when the initial elongation due to tighteningof the twisted components of the load carrying members under loadbecomes significant, lowering of belt tension in the initial runningstages may likewise become significant. This may cause a change in toothpitch and defects such as tooth cracking caused by uneven abrasion of acloth layer over the teeth. This low tension condition may make thesebelts more prone to these defects than a similarly constructed beltoperating under a higher, targeted tension.

Still further, a change in tension in the load carrying members due toinitial elongation may cause a significant change in their diameters.This may lead to detachment of the load carrying members from thematerial in which they are embedded.

Both problems are related in a manner whereby attempting to solve onemay aggravate the other. For example, by increasing the twisting numberof the load carrying members to avoid compromising of the bendingfatigue characteristics, the initial elongation may become detrimentallysignificant. On the other hand, when the twisting number is decreased inorder to reduce initial elongation, bending fatigue properties may beworsened.

With systems incorporating toothed belts, as described above, commonlythe belts will be trained around at least two pulleys. Since such beltsdo not drive, and are not driven, through frictional forces generatedbetween the side surfaces of the belt and cooperating pulley surfaces,and thus do not require a radially projecting flange surface for forcetransmission, at least one of the pulleys must be designed to confineaxial drifting of the power transmission belt relative to thecooperating pulleys in operation.

Heretofore, pulleys in this environment have been made with spacedflanges that have surfaces that bound a space within which the width ofthe toothed power transmission belt resides. The flange surfaces arecomplementary in shape to the facing surfaces on the power transmissionbelt. This can lead to an undesirable degree of noise generation as thebelt repeatedly moves into and out of engagement with the pulleys andcontacts the flange surfaces over a substantial area.

This problem is particularly significant in open systems, such as onmotorcycles, wherein there is no barrier to sound between thecooperating belt and pulleys and the operator of the vehicle.

Heretofore, the industry has not devised a belt construction thatadequately enhances durability and belt life by effectively addressingboth of the above problems through the selection of thickness, twistingnumber, etc. of load carrying members. Further, the industry has noteffectively addressed the problem of noise generation resulting fromcontact between the belt side surfaces and pulley flange surfaces asbelt portions move against and away from the flanges in use.

SUMMARY OF THE INVENTION

In one form, a power transmission belt has a body with a length, a widthbetween laterally spaced sides, and a thickness between inside andoutside surfaces. The body is made at least partially of rubber and hasat least one embedded load carrying member extending in a lengthwisedirection. The body has a plurality of teeth spaced along the body on atleast one of the inside and outside of the body. The teeth have a widththat decreases progressively from: a) a first location between theinside and outside surfaces; and b) one of the inside and outsidesurfaces. The at least one of the inside and outside of the body has asurface that is covered by a cloth layer. The cloth layer: a) has afirst surface applied to the belt body and a second surface exposed toengage a cooperating pulley; and b) is a multiwoven structure with awarp and at least two wefts that are interwoven.

In one form, the warp is made from polyamide fiber and at least one ofthe two different wefts exposed at the second surface is made fromfluorine base fiber.

In one form, the weft fibers on the first surface are not fluorine basedfibers.

In one form, the warp is made from nylon fiber and at least one of thetwo different wefts exposed at the second surface is made from fluorinebased fiber.

In one form, a first type of fiber that softens or melts at atemperature at which the body is vulcanized is extended around thefluorine based fiber by at least one of (a) twisting the first type offiber and fluorine based fiber together; and (b) causing the first typeof fiber to soften or melt and thereby form around part or all of thefluorine based fiber.

In one form, the first type of fiber is at least one of: (a) polyamidebased fiber; (b) polyester based fiber; and (c) olefin based fiber.

In one form, the at least one load carrying member has an inside edgeand an outside edge and the body has a constant width between the insideand outside edges.

In one form, the teeth are on the inside of the body and the firstlocation is spaced from the inside edge of the at least one loadcarrying member towards the inside surface of the body.

In one form, the body has a width that decreases progressively between:a) a second location between the inside and outside surfaces; and b) theother of the inside and outside surfaces.

In one form, the body has a constant width between the first and secondlocations.

In one form, the at least one load carrying member has inside andoutside edges and a thickness between the inside and outside edges. Atleast one fabric layer has a portion between: a) adjacent teeth; and b)one of the inside and outside edges of the at least one load carryingmember and the one of the inside and outside surfaces, and the powertransmission belt has a dimensional relationship of components asfollows:(A+B)−X<Z<(A+B)+Xwhere X=(A+B)×0.35 and

-   A=a distance between: a) one of an inside and outside surface of the    at least one fabric layer that faces away from the at least one load    carrying member; and b) the one of the inside and outside surfaces    of the body;-   B=a thickness of the at least one fabric layer; and-   Z=a distance between the first location and the one of the inside    and outside surfaces of the body.

In one form, the second location is between the at least one fabriclayer and the at least one load carrying member.

In one form, the power transmission belt has a center plane that bisectsthe belt body in a widthwise direction and the body has side surfaceportions between the first location and the one of the inside surfacesthat each makes a first angle with respect to the center plane that isnot greater than 30°.

In one form, the power transmission belt is provided in combination witha first pulley having a central operating axis and a center plane thatis substantially coincident with the center plane of the operativelyassociated power transmission belt. The first pulley has spaced flangesdefining laterally spaced surfaces between which the power transmissionbelt resides with the power transmission belt operatively associatedwith the first pulley. The laterally spaced flange surfaces have firstsurface portions between which the operatively associated powertransmission belt resides that each makes a second angle with respect tothe center plane of the first pulley that is less than the first angle.

In one form, the first pulley has laterally spaced second surfaceportions between which the operatively associated power transmissionbelt resides, each extending substantially parallel to the centerplanes. Each of the first surface portions transitions to one of thesecond surface portions at a first radial location on the first pulley.

In one form, the first location resides radially inside of the firstradial location with the power transmission belt operatively associatedwith the first pulley.

In one form, at least a part of the at least one load carrying memberresides radially inside of the first radial location with the powertransmission belt operatively associated with the first pulley.

In one form, the at least one load carrying member resides fullyradially inside of the first radial location with the power transmissionbelt operatively associated with the first pulley.

In one form, the power transmission belt is provided in combination witha motorcycle into which the first pulley and a second pulley areincorporated. The power transmission belt is trained around the firstand second pulleys.

In one form, the power transmission belt is provided in combination witha first pulley having a central operating axis and spaced flangesdefining laterally spaced surfaces between which the power transmissionbelt resides with the power transmission belt operatively associatedwith the first pulley. The laterally spaced surfaces are configured sothat the teeth do not contact the laterally spaced surfaces over atleast a majority of a distance between the first location and the one ofthe inside and outside surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary, perspective view of one form of toothed powertransmission belt, made according to the present invention;

FIG. 2 is a schematic representation of a toothed power transmissionbelt, made according to the present invention; and

FIG. 3 is a cross-sectional view of a load carrying member on the powertransmission belt of FIG. 1;

FIG. 4 is a cross-sectional view of one modified form of powertransmission belt, according to the present invention, shown operativelyassociated with a pulley;

FIG. 5 is a view as in FIG. 4 with a modified form of power transmissionbelt and pulley;

FIG. 6 is a schematic representation of a system incorporating separatepulleys around which the inventive power transmission belt is trained;and

FIG. 7 is a schematic representation of one particular system, as shownschematically in FIG. 6, in the form of a motorcycle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, a toothed power transmission belt, made according to thepresent invention, is shown at 10. The power transmission belt 10 has abody 12 with a length, extending in the direction of the double-headedarrow L, and width W, between laterally spaced sides 14, 16. The body 12has an inside 18 and an outside 20. The designations “inside” and“outside” are arbitrary as they could be reversed.

The body 12 is made from a rubber composition and includes at least oneembedded load carrying member 22 extending in a lengthwise direction.The load carrying member(s) 22 may be a spirally wrapped singlecomponent or a plurality of components spaced laterally from each other.For purposes of explanation herein, the load carrying members 22 will beconsidered to be plural members, whether made from a single componentwith spaced turns or multiple, separate, laterally spaced components.

The belt body 12 is made with two different sections—a back section 24in which the load carrying members 22 are embedded, and a toothedsection 26. In the toothed section 26, a plurality of laterallyextending teeth 28 are formed. The teeth 28 are trapezoidally shapedfully between the sides 14, 16 and are spaced at regular intervals alongthe belt length L.

The inside 18 of the belt 10 has a surface 30 that is covered by a clothlayer 32. Thus, the cloth layer is applied over the teeth 28.

While the belt 10 is shown with teeth 28 on only one of the inside andoutside of the belt body 12, as shown in FIG. 2, it is contemplated thata toothed belt 10′ might be made according to the invention with a body12′ having teeth 28′ on both a corresponding inside 18′ and outside 20′of a body 12′. The description herein below will be limited to the powertransmission belt 10 shown in FIG. 1.

The rubber composition used for the belt body 12 is selected to havegood resistance to deterioration at elevated temperatures. Exemplaryrubbers suitable for this purpose are hydrogenated nitrile rubber(HNBR), chlorosulfonated polyethylene (CSM), alkylated chlorosulfonatedpolyethylene (ACSM) and chloroprene rubber.

It is preferred that the hardness of the rubber in which the teeth 28are formed be in the range of 89° to 97° in terms of the JIS-A hardness.It is also preferred that the modulus be not less than 5 MPa at 50%elongation. A suitable high modulus rubber is a blended product of HNBRwith a highly fine dispersion of zinc polymethacrylate in HNBR (such as“ZSC”, a trademark used on a commercial product offered by Nippon Zeon)followed by reinforcement as through the addition of silica, carbonand/or short fibers. As a result, the modulus of the belt body 12 isenhanced to maintain engagement of the teeth 28 with a cooperatingpulley 34, even under high load running conditions.

The load carrying members 22 in the back section 24 of the body 12 areembedded in the rubber and extend lengthwise in aligned relationship sothat there is a consistent widthwise spacing between adjacent loadcarrying members 22.

Each load carrying member 22, as seen in FIG. 3, has a twistedconstruction of large diameter made from undertwisted cords 36, in turnmade from twisted chemical fiber 38. The chemical fiber 38 may be, forexample, any of PBO (poly-p-phenylene benzobisoxazal) fiber,polyallylate fiber, aramid fiber, carbon fiber, etc.

Preferably, each load carrying member 22 has a cross-sectional diameterin the range of 1.10 to 1.70 mm² per 1 mm width of the belt body 12.More preferably, this range is 1.10 to 1.66 mm². However, since thereare manufacturing variances and potentially variations resulting fromimprecise measurement of the cross-sectional area, the upper limit maybe 1.70 mm².

It has been found that when the cross-sectional area of the loadcarrying members 22 is maintained within this range, the problemsmentioned previously, that result from initial elongation, arecontrolled, whereby there is no significant detrimental effect onbending fatigue characteristics or resulting from any tightening of thetwisting of the load carrying members. Accordingly, a power transmissionbelt may be constructed that remains durable while operating under highloads.

It is further preferred to use a load carrying member 22 with a twistmultiplier (K) for a plurality of cords 36 that is maintained in therange of 1.5≦K≦2.5, with K=T×D^(1/2)/960 where:

T (times/m)=twist number for the load carrying member(s); and

D (tex) is a thickness of the cords 36.

When the twist multiplier K for the load carrying member 22 is withinthis range, the aforementioned problems associated with initialelongation, notably compromising of bending fatigue characteristics andtightening of twists, can be controlled to the point that the resultingtoothed belt remains adequately durable operating under high loadconditions.

Generally, when the load carrying members 22 are closely aligned in thewidthwise direction of the belt body 12, the belt modulus becomes high.It is preferred that an occupying rate (R) for the load carrying members22 be not less than 75%, with R=n×Dc/B×100 where:

-   -   n=number of load carrying members 22 aligned along the width of        the body 12;    -   Dc (mm)=diameter of load carrying member(s) 22; and    -   B (mm)=width of the body 12.

The characterization “diameter of the load carrying members” as usedherein is intended to mean a diameter measured with the load carryingmembers 22 embedded in the belt body 12.

When the occupying rate R is maintained at not less than 75%, it ispossible to make a toothed power transmission belt with a high modulusand one that is at the same time capable of maintaining engagement witha cooperating toothed pulley, even when operating under high loads.

It is also preferred that the distance/pitch between load carryingmembers 22 in the widthwise direction be not more than the diameter ofthe load carrying members 22 in an untensioned state. The designation“untensioned state” is intended to mean a state of the load carryingmembers 22 in which they are not embedded in the belt body 12 and thereis minimal tension on the load carrying members 22. This can bequantified by characterizing this state as one wherein the tension isnot more than 4.9 N (0.5 kgf). When the lateral spacing between loadcarrying members 22 is maintained as such, the load carrying members 22are densely aligned in such a manner that the belt 10 may have anadequately high modulus.

The cloth layer 32 may be a fiber textile made by weaving of warps 40,extending widthwise of the belt body 12, and wefts 42, extendinglengthwise of the belt body 12. The fiber textile may be plain textile,twilled textile, satin textile, etc. The fiber material making up thefiber textile may be, for example, aramid fiber, urethane elastic yarn,aliphatic fiber yarn (Nylon 6, Nylon 66, polyester, polyvinyl alcohol,etc.) and the like.

Preferably, the fiber textile is a multiple ply, multi-/double wovenstructure made up of at least two different kinds of wefts 42, havingdifferent compositions, and one kind of warp 40 that are woven together.It is preferred to use nylon fiber for the warp 40 and at least one of afluorine based fiber, a nylon fiber, and a urethane elastic yarn for thewefts 42.

With respect to the weft 42 that is on the side 44 of the cloth layer 32that is exposed directly to the pulley 34, it is preferred to use afluorine based fiber, such as PTFE fiber, that accounts for a lowcoefficient of friction between the cloth layer 32 and the cooperatingpulley 34.

The weft 42 exposed on the oppositely facing side 46 of the cloth layer32, that is applied to the surface 30, is made preferably from fiberthat is other than a fluorine based fiber. This fiber is selected sothat the adhering forces between the cloth layer 32 and the rubber onthe surface 30 is adequate. Suitable materials for the weft 42 are nylonfiber, urethane elastic yarn, etc.

In one preferred form, low melting point fiber, that melts or softens ata vulcanizing temperature for the rubber in the body 12, may be formedaround the fluorine based fiber. More specifically, a fluorine basedfiber and a low melting point fiber, as discussed above, may be twistedtogether. Alternatively, a fluorine based fiber may be covered by such alow melting point fiber, as a result of that fiber being melted orpartially melted and thereby formed around part or all of the fluorinebased fiber.

There is no particular limitation with respect to how vulcanization iscarried out for the belt body 12, in terms of either temperature ortime. The vulcanization process may be dictated by taking intoconsideration the type of vulcanizing agent or vulcanizing promoter, aswell as the vulcanizing means, etc., and further by referring to avulcanization curve usually measured by the use of a Mooney viscometeror other measuring device for the vulcanization process. Generallyvulcanization is carried out with temperature maintained in the range of100°-200° C. with a vulcanization time of one minute to five hours.Secondary vulcanization may be carried out, if necessary.

If the low melting point fiber that extends around the fluorine basedfiber is one that softens or melts at the vulcanization temperature forthe belt body, during vulcanization, the fiber flows into the gapsbetween the fibers making up the cloth layer 32, after which the lowmelting point fiber becomes crystallized. As a result, upon engagementof the cloth layer 32 with, or disengagement of the cloth 32 from, thepulley 34 during operation, cutting and scattering of the fluorine basedfiber due to shock and abrasion at the exposed side 44 can be adequatelylimited. As a consequence, the body 12 remains protected for anacceptable use period and premature attachment of teeth 28 from the body12 may be avoided. As a result, a belt with a long life may be produced,even if it is operated at high loads.

Suitable low melting point fibers are, for example, a polyamide basedfiber, a polyester based fiber, or an olefin based fiber.

In the event that a polyamide based fiber is used, it is preferred thatone be used which is copolymerized polyamide that is a combination of aw-amino carboxylic acid component or a dicarboxylic acid component witha diamine.

In the event that a polyester based fiber is used, those with acomposite core-sheath type of fiber are preferred. Examples of polyesterpolymers which are core components having a melting point higher thanthe vulcanization temperature of the belt body are polyethyleneterephthalate, polybutylene terephthalate and a copolymer thereof.

Copolymerized polyester sheath components, having a melting point lowerthan the vulcanization temperature of the body, are produced by apolycondensation reaction of a dibasic acid with a diol. Examplesthereof are those where terephthalic acid and diethylene glycol arebases with a copolymerizing component such as isophthalic acid, adipicacid, sebacic acid, diethylene glycol, butanediol, hexanediol,polyethylene glycol and neopentyle glycol. The melting point may beselected by changing the component combination and copolymerizing ratiothereof.

Examples of the olefin based fiber are polypropylene fiber andpolyethylene fiber (such as high-density polyethylene fiber,medium-density polyethylene fiber, low-density polyethylene fiber,linear low-density polyethylene fiber and ultrahigh-molecularpolyethylene fiber). Substances produced by copolymerization of theabove substances may be used as well. Additionally, there is noparticular limitation as to a twisting method or the fiber constitution,so long as the fiber is softened or melted at the vulcanizationtemperature for the belt body 12.

Additionally, a plasma treatment, or the like, may be carried out on thesurface of the low melting point fiber to enhance the affinity thereofto an adhesive treating agent.

The cloth layer 32 may be adhered to the surface 30 through thefollowing steps.

Step 1

The fiber textile making up the cloth layer 32 is impregnated with aresorcinol-formalin-rubber latex treating solution (hereinafter “RFLtreating solution”) and dried. It is preferred that an aqueousdispersion of a sulfur compound, at least one vulcanizing aid fromamongst a quinone oxime based compound, a methacrylate based compoundand a maleimide based compound, or a dispersion of such a vulcanizingaid in water, be added to the RFL treating solution.

For an aqueous dispersion of a sulfur compound, an aqueous dispersion ofsulfur or tetramethylthiuram disulfide may be used. A suitable exampleof the quinine oxime based compound is p-quinone dioxime. Suitableexamples of the methacrylate based compound are ethylene glycoldimethacrylate or trimethylolpropane trimethacrylate. Suitable examplesof the maleimide based compound are N,N′-m-phenylenebismaleimide orN,N′-(4,4′-diphenylmethanebismaleimide).

Water, in which the vulcanizing aid is dispersed, may contain somealcohol, such as methanol. The affinity of the vulcanizing aid to wateris enhanced even when the vulcanizing aid is insoluble in water wherebythe vulcanizing aid is apt to be dispersed.

If a vulcanizing aid is added to the RFL treating solution, thefollowing effects may be expected. A chemical bond between layers of arubber latex component and an outer layer rubber (this means: (a) amucilage or rolled rubber formed by a mucilage through the treatmentStep 2, below, or by a coating treatment of Step 3, below; or (b) rubberwhich makes up the teeth 28 when the coating treatment is omitted)contained in the RFL treating solution is enhanced. As a result,adhesive force is improved, minimizing the likelihood that the clothlayer 32 will detach from the surface 30.

It is further expected that the chemical bond (cross-linking force) ofthe rubber latex component contained in the RFL treating solution willbe enhanced. As a result, detachment of the outer layer rubber notedabove, due to breakage, takes place before detachment of any separatecushion rubber layer in which the load carrying members are embedded,due to cohesion failure, i.e., interlayer detachment.

In the event that a vulcanizing aid is added to the RFL treatingsolution, an impregnating treatment of the fiber textile may be carriedout in two treatment steps. The above-mentioned vulcanizing aids are notadded to the RFL treating solution in the first dipping treatment intothe RFL treating solution. That is because in the first treating step,hardening of RF is to be carried out prior to cross-linking of therubber latex component.

In the second RFL impregnating treating step, an RFL treating solutionis used that contains more rubber latex component than the first RFLtreating solution and is added to: (a) an aqueous dispersion of a sulfurcompound; (b) at least one vulcanizing aid from amongst: (i) quinoneoxime based compound; (ii) a methacrylate based compound; and (iii) amaleimide based compound; or (c) an aqueous dispersion of thevulcanizing aid in water.

The reason there are different amounts of rubber latex component in theRFL treating solution in the first and second impregnating treatmentsteps is to enhance the adhesive property of the RFL layer to both thefiber and rubber, that have different affinities.

Step 2

Two kinds of mucilage treatments (P1 and S1 treatment) are carried outin which the fiber textile is adhered with an adhesive treating agent,made up of mucilage wherein a rubber composition is dissolved in asolvent, and then subjected to a baking treatment.

Step 3

Mucilage and rolled rubber are coated onto the surface of the fibertextile, in a coating treatment process. The mucilage and rolled rubberbecome coated upon the fiber textile and then to the underlying teeth28.

In the event that a vulcanizing aid is added to the RFL treatingsolution, it is preferably the same vulcanizing aid as added to therolled rubber and the mucilage used in the coating treatment. As aresult, significant improvements may be expected in: (a) adhesionbetween the mucilage and the fiber textile treated with the RFL treatingsolution; (b) adhesion between the rolled rubber and fiber textiletreated with the RFL treating solution; and (c) adhesion between therolled rubber, mucilage and fiber textile treated with the RFL treatingsolution.

It is not necessary to conduct all of the above treatment steps.Preferably, at least one or two of these steps are performed. Forexample, when a vulcanizing aid is added to the RFL treating solution inthe treatment Step 1, adhesion between the rubber and the fiber textileis considerably enhanced. Thus, the mucilage treatment in Step 2 may beomitted.

A durability test was conducted using a biaxial high-load running testto ascertain the benefits of the present invention.

The test conditions were as follows:

Tester: Biaxial high-load running tester;

Evaluated belt size: 130H14M 20 (tooth number: 130; tooth type: H14M;belt width: 20 mm);

Tooth number of the driving pulley: 33;

Tooth number of the driven pulley: 61;

Set tension: 550 N;

Speed: 1,200 rpm; and

Load: Any of 626 Nm (running condition 1); 554 Nm (running condition 2);and 480 Nm (running condition 3) on the driven pulley.

The rubber composition, constitution of the load carrying members, andcloth layer constitution used in the durability tests are shown inTables 1, 2 and 3, respectively.

TABLE 1 Rubber Composition Rubber Composition R-0 R-1 R-2 HNBR *1 50 5050 Composite Polymer of Metal Unsaturated 50 50 50 Carboxylate with HNBR*2 Aromatic Amide Fiber *3 0 5 10 Plasticizer *4 5 5 5 Stearic Acid 1 11 Zinc Oxide 5 5 5 Silica *5 25 50 50 Anti-Aging Agent *6 1 1 1Vulcanizing Aid *7 2 2 2 Organic Peroxide *8 2 2 2 Hardness (JIS-A) 8994 96 MSO (Modulus uon 50% Elongation) (unit: MPa) 5.0 8.0 11.0 *1“Zetpol 2020” manufactured by Nippon Zeon *2 “ZSC 2295 N” manufacturedby Nippon Zeon *3 “Cornex Short Fiber” manufactured by Teijin *4 “AdekaSizer RS 700” manufactured by Asahi Denka *5 “Ultrasil VN 3”manufactured by Degussa Japan *6 “Nocrac MBO” manufactured by OuchShinko Kagaku *7 “San Ester TMP” manufactured by Sanshin Kagaku Kogyo *840 wt % of 1,3-Bis(tert-butylperoxyisopropyl)benzene and 60 wt % ofcalcium carbonate

TABLE 2 Load Carrying Member Constitution G-0 A-1 A-2 A-3 A-4 A-5 C-1Fiber Material Glass Aramid Aramid Aramid Aramid Aramid Carbon FiberUnder Yarn Size (unit: tex) 33.7 167 167 167 167 167 800 Consitution9/17 1/24 1/24 1/20 1/18 3/6 4/0 Twist Multiplier (K) 3.0 1.5 2.5 2.52.0 2.0 2.4

TABLE 3 Cloth Layer Constitution F-1 F-2 F-3 F-4 F-5 Twisted 2/2 TwilledWeft: 2 colors, Weft: 2 colors, Weft: 2 colors, Weft: 2 colors,Constitution double woven; double woven; double woven; double woven;Front: 1/3 Front: 1/3 Front: 1/3 Front: 1/3 Twilled; Back: Twilled;Back: Twilled; Back: Twilled; Back: 2/2 Twilled 2/2 Twilled 2/2 Twilled2/2 Twilled Warp Nylon 66 Nylon 66 Nylon 66 Nylon 66 Nylon 66 Weft-1Nylon 66; PTFE Fiber *1; PTFE Fiber *1; PTFE Fiber *1; PTFE Fiber *1;Urethane Urethane Polyester Polyamide Olefin Elastic Yarn Elastic Yarnbased fiber *2; based fiber *3; based fiber *4; Urethane UrethaneUrethane Elastic Yarn Elastic Yarn Elastic Yarn Weft-2 Nylon 66; Nylon66; Nylon 66; Nylon 66; Urethane Urethane Urethane Urethane Elastic YarnElastic Yarn Elastic Yarn Elastic Yarn *1: PTFE fiber: Toyoflon 1330dtex manufactured by Toray *2: Polyester based fiber: “Cornetta”manufactured by Unitika *3: Polyamide based fiber: “Flor M” manufacturedby Unitika *4: Olefin based fiber: “Dainima” manufactured by Toyobo

As shown in Table 3, the weft of F-2 is made with PTFE fiber, which is afluorine based fiber. With the F-3, F-4 and F-5 cloth layers, inaddition to the PTFE fiber, low melting point fiber that softened ormelted at the rubber vulcanizing temperature, i.e., polyester basedfiber, polyamide based fiber and olefin based fiber, were respectivelyincorporated. The rubber of the belts used in this test was vulcanizedat a temperature of 165° C. for 30 minutes. With the polyester basedfiber (“Cornetta” manufactured by Unitika), the melting point of thecore was 256° C. and that of the sheath was 160° C. In the polyamidebased fiber (“Flor M” manufactured by Unitika), the melting point was135° C. In the olefin based fiber (“Dainima” manufactured by Toyobo),the melting point was 140° C.

The compositions of the RFL treating solution, the mucilage treatment(P1 treatment and S1 treatment) and rubber for the coating treatment forthe cloth layer adhesive treatment are shown in Tables 4, 5 and 6,respectively.

TABLE 4 RFL Composition B-1 B-2 HNBR Latex (40 wt %) *1 100 100 RFCondensate (20 wt %) *2 50 25 Aqueous Solution of NaOH (10 wt %) 2Dispersion of Maleimide based compound (50 wt %) 20 Water 110 100 *1Latex manufactured by Nippon Zeon *2 Molar ratio of R/F = 1/1.5 (forB-1, it is 1/1)

TABLE 5 Composition for PT Treatment (treatment with mucilage containingisocyanate); and composition for S1 Treatment (treatment with mucilage)Composition Mucilage for P1 Mucilage for S1 Composition for HNBRMucilage 5 15 Polymeric MDI 5 MEK 90 85

TABLE 6 Composition of Rubber for Coating Treatment Composition ofRubber C-1 C-2 HNBR *1 100 HNBR *2 50 HNBR *3 50 Zinc Oxide 2 2Magnesium Oxide 4 Stearic Acid 1 1 Silica 50 Carbon Black 50 0Anti-Aging Agent 2 2 Vulcanizing Aid *4 2 2 Organic Peroxide *5 2 2Plasticizer (Polyether Type) 5 10 *1 “Zetpol 2020” manufactured byNippon Zeon *2 “Zetpol 2010L” manufactured by Nippon Zeon *3 “ZSC 2295N” manufactured by Nippon Zeon *4 “Maleimide based compound *5 40 wt %of 1.3-bis(tert-butylperoxyisopropyl)benzene and 60 wt % of calciumcarbonate

In Tables 1 to 6, the units are wt % and the oblique lines in Tables 4-6indicate that there is no addition or no treatment unless otherwisementioned.

Fourteen kinds of belts, made with rubber compositions, load carryingmember constitution, tooth cloth layer constitution and using toothcloth layer adhesive treatments, as set out in Tables 1 to 6, weresubjected to a durability test under the above-mentioned testconditions. The results are shown in Tables 7 and 8, below.

TABLE 7 Test Result (1) TG-1 TG-2 TG-3 TG-4 TG-5 TG-6 TG-7 ComparativeInventive Inventive Inventive Inventive Inventive Inventive EvaluatedBelt Example Example Example Example Example Example Example RubberComposition R-0 R-0 R-0 R-0 R-0 R-1 R-1 Load Carrying Member G-0 G-0 A-1A-2 A-3 A-3 A-3 Cloth Layer F-1 F-3 F-1 F-1 F-1 F-2 F-2 AdheringTreatment for Toothed Belt RFL (first step) B-1 B-1 B-1 B-1 B-1 RFL(second step) B-2 P1 Treatment conducted or conducted or conducted orconducted or conducted or conducted or not adopted adopted adoptedadopted adopted adopted conducted/ not adopted S1 Treatment conducted orconducted or conducted or conducted or conducted or conducted or notadopted adopted adopted adopted adopted adopted conducted/ not adoptedCoating Treatment C-1 C-1 C-1 C-1 C-1 C-1 C-1 Initial Molding not notnot not not not not conducted/ conducted/ conducted/ conducted/conducted/ conducted/ conducted not adopted not adopted not adopted notadopted not adopted not adopted or adopted Load Carrying Member Pitch(mm) 2.87 2.87 2.95 2.95 2.85 2.8 2.4 Load Carrying Member Diameter 2.452.45 3.01 2.83 2.55 2.55 2.55 (without tension) (mm) Load CarryingMember Diameter 1.92 2.01 2.20 2.24 2.09 2.00 2.25 (in a belt) (mm)Width of Belt (mm) 20 20 20 20 20 20 20 Cross Section of (mm²/ 2.9 3.163.81 3.92 3.36 3.78 3.78 Load Carrying Member load carrying member)(mm²/mm belt) 1.01 1.10 1.29 1.33 1.16 1.12 1.66 Occupying Rate of LoadCarrying Member (%) 58 60 86 67 63 70 90 Effective Load Carrying MemberNumber 6 6 6 6 6 7 8 Load Carrying Member Diameter 11.5 12.0 13.2 13.412.5 14.0 18.0 (in belt) × Effective Load Carrying Member Life underRunning Condition 1 (hours) 35 Life under Running Condition 2 (hours)205 480 Life under Running Condition 3 (hours) 30 322 177 120 222 734

TABLE 8 Test Result (2) TG-8 TG-9 TG-10 TG-11 TG-12 TG-13 TG-14Comparative Inventive Inventive Inventive Inventive Inventive InventiveEvaluated Belt Example Example Example Example Example Example ExampleRubber Composition R-1 R-1 R-1 R-1 R-2 R-2 R-2 Load Carrying Member A-3A-3 A-3 A-3 A-4 A-5 C-1 Cloth Layer F-2 F-4 F-5 F-3 F-3 F-3 F-3 AdheringTreatment for Toothed Belt RFL (first step) B-1 B-1 B-1 B-1 B-1 B-1 B-1RFL (second step) B-2 B-2 B-2 B-2 B-2 B-2 B-2 P1 Treatment not not notnot not not not conducted conducted conducted conducted conductedconducted conducted S1 Treatment not not not not not not not conductedconducted conducted conducted conducted conducted conducted CoatingTreatment C-2 C-2 C-2 C-2 C-2 C-2 C-2 Initial Molding adopted adoptedadopted adopted adopted adopted adopted Load Carrying Member Pitch (mm)2.3 2.3 2.3 2.3 2.3 2.3 2.3 Load Carrying Member Diameter 2.55 2.55 2.552.55 2.40 2.45 2.10 (without tension) (mm) Load Carrying Member Diameter2.10 2.15 2.11 2.19 2.03 2.05 1.86 (in a belt) (mm) Width of Belt (mm)20 20 20 20 20 20 20 Cross Section of Load Carrying Member (mm²/loadcarrying 3.46 3.63 3.50 3.77 3.24 3.30 2.78 member) (mm²/mm belt) 1.511.58 1.52 1.64 1.41 1.44 1.21 Occupying Rate of Load Carrying Member (%)84 86 84 88 81 82 75 Effective Load Carrying Member Number 8 8 8 8 8 8 8Load Carrying Member Diameter 16.8 17.2 16.9 17.5 16.2 16.4 15.0 (inbelt) × Effective Load Carrying Member Life under Running Condition 1(hours) 155 256 320 289 970 1250 1850 Life under Running Condition 2(hours) 550 Life under Running Condition 3 (hours)

Belts TG-1 to TG-5 showed relatively low durability among the 14 kindsof belts (TG-1 to TG-14) based on the low-load testing (runningcondition 3). Test results under high load (running conditions 1 and 2)are omitted. On the other hand, belts TG-8 to TG-14 showed relativelyhigh durability as a result of a high-load testing (running condition 1or 2). Test results under lower load (running condition 2 or 3) areomitted.

As seen in Tables 7 and 8, characteristics for the load carrying memberssuch as pitch, cross section and occupying rate, were different for the14 kinds of belts.

The cross sections of the load carrying members per mm width of thebelts in Tables 7 and 8 were calculated by the following formula.

Load carrying member cross section per 1 mm belt width (mm²/mm)belt)=(belt width (mm)/load carrying member pitch (mm))×load carryingmember cross section per load carrying member (mm²/core wirenumbers)÷belt width (mm)=load carrying member cross section per loadcarrying member (mm²/load carrying member number)/load carrying memberpitch (mm²).

To determine the load carrying member cross section per load carryingmember (mm²/load carrying member numbers), the load carrying membercross section is calculated from an SEM image analysis of the beltsection (tooth head) and then averaged based upon the total loadcarrying member number (n). To determine the load carrying member pitch(mm), the distance between load carrying member centers of a beltsection is measured at ten places and then averaged. However, in theevent the belt width is narrow and measurement at ten places is notpossible, measurement at five places, followed by averaging, is carriedout. The distance between load carrying member centers was measuredusing known devices such as an SEM and a projector.

Load carrying member occupying rate (R) (%) is calculated by thefollowing formula.

Load carrying member occupying rate (%)=effective load carrying membernumber (n)×load carrying member diameter (Dc) (mm)÷belt width (B)(mm)×100.

The effective load carrying member number (n) is the number of loadcarrying members aligned in the width direction of the belt. In Tables 7and 8, the belt width (B) is divided by load carrying member pitch. Allnumbers after the decimal point are omitted.

In Tables 7 and 8, the term “Initial Molding” is used to identifywhether or not an “initial molding method” was adopted in the step forthe manufacture of a belt. The “initial molding method” is a methodwhere, after the cloth layer and teeth are first/initially molded usinga mold having a toothed profile, unvulcanized rubber containing the loadcarrying members and the back sections are wrapped around the mold.Thereafter, this subassembly is vulcanized using a vulcanizing can. Inthis initial molding method, since the cloth layer and teeth are moldedbefore vulcanization, it is not necessary upon vulcanization to flow theunvulcanized rubber, making up the back section, into/through the spacebetween the load carrying members. Therefore, it is possible to make thedistance between the load carrying members (pitch) narrow. Accordingly,as previously mentioned, this initial molding method is suitable forpreparation of a high modulus belt where the pitch is relatively small,i.e., not larger than the load carrying cord diameter in an untensionedstate (belts TG-7 to TG-14 in Table 7).

As shown in Tables 7 and 8, for belt TG-1 of the Comparative Example,where the cross section of the load carrying member per 1 mm of the beltis small (<1.10), belt trouble resulted within about 30 hours even underthe running condition 3 where the load is the lowest. Thus, durabilitywas considerably low. On the contrary, in the case of belts TG-2 toTG-5, where the load carrying member cross section is more than that ofthe belt TG-1 and the twist multiplier of the load carrying member iswithin a range of 1.5≦K≦2.5 (refer to Table 2), not less than a fourtimes longer life was achieved under the same running condition 3 and,therefore, the durability was shown to be improved.

In the belts TG-2 and TG-6 to TG-14, where different tooth cloths (toothcloth (F-2 to F-5) as a multi-woven structure with warp and twodifferent kinds of weft) from the tooth cloths of the belts T-1 and TG-3to TG-5 were used, it can be seen that, under the running condition 1 or2 with higher load, life of not shorter than 200 hours was achieved,evidencing better durability than belts TG-1 and TG-3 to TG-5.

In belts TG-9 to TG-11, although conditions thereof other than toothcloth are nearly the same as those of TG-8, life of not less than 1.6times was achieved under the high load running condition 1. That isbecause, in belt TG-8, a tooth cloth F-2, using no low melting pointfiber in the weft was used while, in belts TG-9 to TG-11, low meltingpoint fiber such as polyester based fiber, polyamide based fiber orolefin based fiber were used in the weft (refer to Table 2). Thus, it islikely that, when a low melting point fiber is provided around thefluorine based fiber (PTFE fiber) of the weft, cutting and scattering ofthe fluorine based fiber are suppressed and the rubber of the belt bodyis able to be protected for a long period of time.

Further, with the belts TG-8 to TG-14, RFL treatment upon adhesion ofthe tooth cloth is conducted in two steps. Moreover, a vulcanizing aidis added in the RFL treating solution during the second step. It islikely that, as a result, adhesive forces of the tooth cloth increaseand there is an enhanced durability, as compared with the belts TG-6 andTG-7, which are not subjected to such a treatment.

Furthermore, for belts TG-7 to TG-14, an initial molding method wasadopted during manufacture. As a result, the load carrying member pitchbecomes smaller than it is with the load carrying cords in theuntensioned state. As such, as compared with the belts TG-1 to TG-6,load carrying members are densely aligned in the width direction of thebelt, whereby the load carrying member occupying rate (R) is high (notless than 75%) and modulus is likewise high and, accordingly, it isexpected that the durability will thereby be enhanced.

Still further, in TG-13 where A-5 is adopted as a load carrying memberconstitution, running life under the running condition 1 is longer thanTG-12 where A-4 is adopted. That is because, in the load carrying memberconstitution of A-5, maintenance of tension is good and tension rises inthe treatment of the load carrying member whereby the initial elongationby tightening the twisting is limited and detachment of teeth resultingfrom elongation of the belt may be limited.

A modified form of power transmission belt, made with the same basiccomponents substantially as set forth above, is shown at 50 in FIG. 4.The power transmission belt 50 has a body 52 with a length, that extendsinto the page, and a width between laterally spaced sides 54, 56. Thebody 52 has a thickness T between an inside surface 58 and an outsidesurface 60.

As in the prior embodiment, the body 52 is made at least partially fromrubber in which at least one load carrying member 62 is embedded. Theload carrying member 62 extends in a lengthwise direction.

The body 52 has teeth 64, as previously described, that are at regularlyspaced intervals along the length of the body 52. As noted with respectto FIG. 2, the teeth 64 may be on either the inside or outside of thebody 52, with the schematic showing in FIG. 2 corresponding likewise tothe power transmission belt 50.

In this embodiment, the teeth 64 are provided at the inside 66 of thebody 52, with no teeth being provided at the outside 68 of the body 52.Again, as noted above, the characterizations “inside” and “outside” arein a certain respect arbitrary since the power transmission belt 50 canbe turned inside out to reverse these relationships.

The teeth 64 have widths that decrease progressively from: a) a firstlocation 70 between the inside and outside surfaces 58, 60; and b) theinside surface 58. The tapering of the width is preferably at a constantangle α from the first location 70 to the inside surface 58. The widthW1 of the inside surface 58 is less than the width W2 of the outsidesurface 60.

In this embodiment, the power transmission belt 50 has at least onecloth/fabric layer 72 applied over the teeth 64 at the inside 66 of thebody 52. An inside edge 74 of the load carrying member 62 is adjacent toa facing/outside surface 76 on the cloth layer 72 on a portion of thecloth layer 72 between adjacent teeth 64.

The load carrying member 62 has a diameter D between the inside edge 74and an outside edge 78. In this embodiment, the body 52 has a constantwidth W over the thickness between the inside and outside edges 74, 78of the load carrying member 62 and fully over the tension section 80that resides outside of a neutral plane P defined at the center of theload carrying member 62 between the inside and outside edges 74, 78thereon.

The first location 70 is spaced from the inside edge 74 of the loadcarrying member 62 towards the inside surface 58 of the body 52.

In one preferred form, the dimensional relationship between componentsis as follows: (A+B)−X<Z<(A+B)+X, where X=(A+B)×0.35 and

A=a distance between: a) one of an inside and outside surface 81 of theat least one cloth layer 72 that faces away from the at least one loadcarrying member 62; and b) the one of the inside and outside surfaces58;

B=a thickness of the at least one cloth layer 72; and

Z=a distance between the first location 70 and the one of the inside andoutside surfaces 58.

The power transmission belt 50 has a center plane CP that bisects thebody 52 in a widthwise direction. Side surface portions 82, 84 aredisposed at the angle α with respect to the center plane CP. α ispreferably not greater than 30°.

The power transmission belt 50 is shown operatively associated with afirst pulley 86 that has a central operating axis and a center planethat is substantially coincident with the center plane CP of theoperatively associated power transmission belt 50. For purposes ofsimplification, the center planes of each of the power transmission belt50 and first pulley 86 will be identified as CP.

The first pulley 86 has spaced flanges 88, 90, respectively, withfacing, laterally spaced surfaces 92, 94 defining a space between whichthe operatively associated power transmission belt 50 resides. Thesurfaces 92, 94 have the same shape and thus description herein will belimited to the exemplary surface 92.

The surface 92 has a surface portion 96 that makes an angle α1 withrespect to the center plane CP. α1 is preferably less than α.

A separate surface portion 98 extends substantially parallel to thecenter plane CP and transitions into the surface portion 96 at a firstradial location 100 that is spaced a radial distance Y outwardly fromthe inside surface 58 of the operatively associated power transmissionbelt 50.

The first location 70 resides radially inside of the first radiallocation 100 with the power transmission belt 50 operatively associatedwith the first pulley 86.

In this embodiment, at least a part of the at least one load carryingmember 62 also resides radially inside of the first radial location 100with the power transmission belt 50 operatively associated with thefirst pulley 86.

In FIG. 5, a modified form of belt, similar to that in FIG. 4, is shownat 50′, with corresponding components similarly numbered with theaddition of a “′” designation. The power transmission belt 50′ has abody 52′ with at least one load carrying member 62′ embedded therein. Acloth layer 72 is applied over teeth 64′ at the inside of the belt body52′.

The power transmission belt 50′ differs from the power transmission belt50 primarily by reason of the body 52′ having a width that decreasesprogressively between: a) a second location 102 between the inside andoutside surfaces 58′, 60′; and b) the outside surface 60′.

The body 52′ has a constant width W3 between the first location 70′ andthe second location 102. As depicted, the width W3 between the firstlocation 70′ and second location 102 is constant over the thickness B′of the cloth layer 72′ at the location between adjacent teeth 64′ andadjacent to the inside edge 74′ of the load carrying member 62′. Theload carrying member 62′ has an outside edge 78′.

The second location 102 is between the outside surface 76′ of theportion of the cloth layer 72′, between adjacent teeth 64′, and theinside edge 74′ of the load carrying member 62′.

The power transmission belt 50′ is operatively associated with a firstpulley 86′ with flanges 88′, 90′. Representative flange 88′ has asurface portion 98′ that is substantially parallel to the center planeCP. The surface portion 98′ blends into a surface portion 96′ at theangle α1 with respect to the center plane CP. The surface portions 98′,96′ transition at a first radial location 100′.

In this embodiment, the load carrying member 62′ resides fully radiallyinside of the first radial location 100′ with the power transmissionbelt 50′ operatively associated with the first pulley 86′.

The pulley flanges 88, 90; 88′, 90′ respectively project radially beyondthe outside surfaces 60, 60′ of the belts 50, 50′ to preventlateral/axial shifting of the power transmission belts 50, 50′ thereoverout of the operatively associated relationship. The relativeconfiguration of components results in there being a limited contactregion between the belt side surfaces 54, 56; 54′, 56′ and the pulleyflange surfaces 92, 94; 92′, 94′.

More specifically, in the case of the power transmission belt 50, thecontact region between the inside and outside surfaces 58, 60 is limitedto that region radially outwardly from the first location 70 to thefirst radial location 100 with the power transmission belt 50operatively associated with the pulley 86, as shown in FIG. 4.

In the FIG. 5 embodiment, the corresponding contact region is limited tothe side surface portions between the first location 70′ and the secondlocation 102.

As a result, the teeth 64, 64′ do not contact the flange surfaces 92,94; 92′, 94′ over at least a majority of a distance between the firstlocation 70, 70′ and the inside surfaces 58, 58′.

In the case of the belt 50, the contact region outside of the firstlocation 70 is further reduced by the angling of the surface portions96. Similarly, the contact region for the belt 50′ radially outwardlyfrom the first location 70′ is reduced by reason of the diminishing ofthe width of the belt body 52′ outside of the second location 102 andadditionally the angling of the surface portions 96′.

By reducing contact area, sound generation can be minimized. Further,the belts 50, 50′ are not as prone to being worn or damaged at theirsides.

It is contemplated that the power transmission belt 50, 50′ may be usedin any system, as shown schematically at 104 in FIG. 6, including afirst pulley 86, 86′, as described, and a second pulley 106, with thepower transmission belt 50, 50′ trained around the first pulley 86, 86′and second pulley 106. The schematic showing of the system 104 isintended to encompass all variations of systems of this general type.

In one preferred application, as shown in FIG. 7, the power transmissionbelt 50, 50′ is provided on a motorcycle 106 having a frame 108supported on spaced wheels 110, 112. The frame 108 supports an engine114 that has either of the pulleys 86, 86′; 106, with the drive wheel112 having the other pulley 86, 86′; 106. The power transmission belt50, 50′ is trained around the pulley 86, 86′; 106 and a cooperatingpulley 86, 86′; 106.

The cloth layers 72, 72′ preferably have the same composition as thecloth layer 32 described above. The other components on the belts 50,50′ likewise may have the same compositions as their counterparts on thebelt 10, as described above.

The foregoing disclosure of specific embodiments is intended to beillustrative of the broad concepts comprehended by the invention.

The invention claimed is:
 1. A power transmission belt comprising: abody having a length, a width between laterally spaced sides, and athickness between inside and outside surfaces, the body comprisingrubber and including at least one embedded load carrying memberextending in a lengthwise direction, the body having a plurality ofteeth spaced along the body on at least one of the inside and outside ofthe body, the teeth having a width dimension extending between thelaterally spaced sides of the body that decreases progressively from: a)a first location between the inside and outside surfaces; and b) one ofthe inside and outside surfaces, wherein the at least one of the insideand outside of the body has a surface that is covered by a cloth layer,wherein the cloth layer: a) has a first surface applied to the belt bodyand a second surface exposed to engage a cooperating pulley; and b)comprises a multiwoven structure comprising a warp and at least twowefts that are interwoven, the at least two wefts having compositionsthat are different, each from the other.
 2. The power transmission beltaccording to claim 1 wherein the warp comprises polyamide fiber and atleast one of the two different wefts exposed at the second surfacecomprises fluorine based fiber.
 3. The power transmission belt accordingto claim 2 wherein the weft fibers on the first surface do not comprisefluorine based fibers.
 4. The power transmission belt according to claim1 wherein the warp comprises nylon fiber and at least one of the twodifferent wefts exposed at the second surface comprises fluorine basedfiber.
 5. The power transmission belt according to claim 3 wherein afirst type of fiber that softens or melts at a temperature at which thebody is vulcanized is extended around the fluorine based fiber by atleast one of (a) twisting the first type of fiber and fluorine basedfiber together; and (b) causing the first type of fiber to soften ormelt and thereby form around part or all of the fluorine based fiber. 6.The power transmission belt according to claim 5 wherein the first typeof fiber comprises at least one of: (a) polyamide based fiber; (b)polyester based fiber; and (c) olefin based fiber.
 7. The powertransmission belt according to claim 1 wherein the at least one loadcarrying member has an inside edge and an outside edge and the body hasa constant width between the inside and outside edges.
 8. The powertransmission belt according to claim 1 wherein the teeth are on theinside of the body and the first location is spaced from the inside edgeof the at least one load carrying member towards the inside surface ofthe body.
 9. The power transmission belt according to claim 1 whereinthe body has a width dimension extending between the laterally spacedsides of the body that decreases progressively between: a) a secondlocation between the inside and outside surfaces; and b) the other ofthe inside and outside surfaces.
 10. The power transmission beltaccording to claim 9 wherein the body has a constant width between thefirst and second locations.
 11. The power transmission belt according toclaim 1 wherein the at least one load carrying member has inside andoutside edges and a thickness between the inside and outside edges,there is at least one fabric layer with a portion between: a) adjacentteeth; and b) one of the inside and outside edges of the at least oneload carrying member and the one of the inside and outside surfaces, andthe power transmission belt has a dimensional relationship of componentsas follows:(A+B)−X<Z<(A+B)+X where X=(A+B)×0.35 and A=a distance between: a) one ofan inside and outside surface of the at least one fabric layer thatfaces away from the at least one load carrying member; and b) the one ofthe inside and outside surfaces of the body; B=a thickness of the atleast one fabric layer; and Z=a distance between the first location andthe one of the inside and outside surfaces of the body.
 12. The powertransmission belt according to claim 9 wherein the at least one loadcarrying member has an inside edge and an outside edge, the body furthercomprising at least one fabric layer between adjacent teeth adjacent oneof the inside and outside edges of the at least one load carryingmember, and the at least one load carrying member resides between thesecond location and the other of the inside and outside surfaces. 13.The power transmission belt according to claim 12 wherein the secondlocation is between the at least one fabric layer and the at least oneload carrying member.
 14. A power transmission belt comprising: a bodyhaving a length, a width between laterally spaced sides, and a thicknessbetween inside and outside surfaces, the body comprising rubber andincluding at least one embedded load carrying member extending in alengthwise direction, the body having a plurality of teeth spaced alongthe body on at least one of the inside and outside of the body, theteeth having a width that decreases progressively from a) a firstlocation between the inside and outside surfaces; and b) one of theinside and outside surfaces, wherein the at least one of the inside andoutside of the body has a surface that is covered by a cloth layer,wherein the cloth layer: a) has a first surface applied to the belt bodyand a second surface exposed to engage a cooperating pulley; and b)comprises a multiwoven structure comprising a warp and at least twodifferent wefts that are interwoven, wherein the power transmission belthas a center plane that bisects the power transmission belt body in awidthwise direction and the body has side surface portions between thefirst location and the one of the inside surfaces that each makes afirst angle with respect to the center plane that is not greater than30°.
 15. The power transmission belt according to claim 14 incombination with a first pulley having a central operating axis and acenter plane that is substantially coincident with the center plane ofthe operatively associated power transmission belt and spaced flangesdefining laterally spaced surfaces between which the power transmissionbelt resides with the power transmission belt operatively associatedwith the first pulley, the laterally spaced flange surfaces having firstsurface portions between which the operatively associated powertransmission belt resides that each makes a second angle with respect tothe center plane of the first pulley that is less than the first angle.16. The power transmission belt according to claim 15 wherein the firstpulley has laterally spaced second surface portions between which theoperatively associated power transmission belt resides and eachextending substantially parallel to the center planes, each of the firstsurface portions transitioning to one of the second surface portions ata first radial location on the first pulley.
 17. The power transmissionbelt according to claim 16 wherein the first location resides radiallyinside of the first radial location with the power transmission beltoperatively associated with the first pulley.
 18. The power transmissionbelt according to claim 17 wherein at least a part of the at least oneload carrying member resides radially inside of the first radiallocation with the power transmission belt operatively associated withthe first pulley.
 19. The power transmission belt according to claim 17wherein the at least one load carrying member resides fully radiallyinside of the first radial location with the power transmission beltoperatively associated with the first pulley.
 20. The power transmissionbelt according to claim 15 in combination with a motorcycle upon whichthe first pulley and a second pulley are provided and the powertransmission belt is trained around the first and second pulleys. 21.The power transmission belt according to claim 1 in combination with afirst pulley having a central operating axis and spaced flanges defininglaterally spaced surfaces between which the power transmission beltresides with the power transmission belt operatively associated with thefirst pulley, and the laterally spaced surfaces are configured so thatthe teeth do not contact the laterally spaced surfaces over at least amajority of a distance between the first location and the one of theinside and outside surfaces.